In general, swash plate compressors are widely used in air conditioning systems for vehicles, and include a piston, a piston driving unit, a cylinder block, and a valve in common.
In such a swash plate compressor, a swash plate whose inclination angle is varied within a crank chamber rotates as its shaft rotates and a piston reciprocates to perform a compressing operation while the swash plate is rotating.
In this case, a refrigerant in a suction chamber is suctioned into a cylinder and is discharged to an exhaust chamber by reciprocal movement of the piston, in which case the inclination angle of the swash plate is varied to control the amount of exhausted refrigerant according to a difference between a pressure within the crank chamber and a pressure within the suction chamber.
As a result, the swash plate compressor suctions the refrigerant from the suction chamber and compresses the refrigerant by means of the piston, and the compressed refrigerant is exhausted to the exhaust chamber to repeat a cooling cycle.
Then, an exhaust check valve for exhausting the compressed refrigerant at a certain pressure and preventing the exhausted gas from reversely flowing to the compressor is installed in an exhaust opening communicated with the exhaust chamber.
In a clutch-less compressor, the exhaust check valve is maintained in a closed state when the compressor is operated below a preset pressure difference (when an air conditioner is switched off or the swash plate is operated with it being inclined by an angle below a certain value) and is opened only when the pressure difference is above a preset pressure difference.
However, in the conventional technology, a small amount of leak gas is generated in a fine gap between a movable member (valve) and a valve body (valve seat) when a compressor is driven below a preset pressure difference and the leak gas passes though the valve body to flow the rear surface of the movable member, making it difficult for the valve to be opened at the predetermined pressure due to a load of a spring on the rear surface of the movable member and a pressure of the leak gas.